Safety switch



July 7, 1953 H. A. LOCEY 2,644,868

SAFETY SWITCH Filed July 3l. 1950 Harry ocef/ l INVENTOR.

Patented July 7, 1953 UNITED SAFETY SWITCH Harry A. Locey, Houston, Tex., assgnor to Lenora H. Allison, Houston, Tex.

Application July 31, 1950, Serial No. 176,789

(Cl. 20D-86) 1 Claim.

The invention relates to a device for cutting off the flow of power to an operating mechanism, and more particularly to a mobile safety switch.

Various devices have been proposed to act as safety switches which automatically cut off the flow of power to an operating mechanism upon the occurrence of some event. For example, in the operation of numerous machines, where such machines are hand fed, it is not an uncommon occurrence for the person operating the machine to get some part of his clothing or some part of his body caught in the machine. The safety switch is provided to cut off the ilow of power to the machine thus lessening the danger to the operator.

It is also desirable to provide a safety switch to cut oli the flow of power when working with and testing electrical equipment. If the flow of electricity becomes short circuited, it is possible for the person testing or Working on the equipment to receive a severe shock which might endanger his life if some means is not provided which stops the flow of power when such event occurs.

The primary disadvantages with various safety f switches heretofore proposed is the fact that customarily, such switches are mounted in a stationary position. This is disadvantageous in that if the foot or hand of the person engages the safety switch while operating the machine it may not always be possible to actuate the 'safety switch or to actuate it as promptly as desired by removing the hand or foot from the switch. The operator is quite often excited when such event occurs and may even forget that a safety means is provided.

The present invention is directed to a safety switch construction which does not rely upon some premeditated positive movement by the perator to cut oif the flow of power to the machine which he is operating or to the apparatus being tested; rather the machine is so constructed that its operation is eiected by the natural movement of the person arising from the excitement surrounding the occurrence of an event for which the safety switch is designed.

The invention is also designed to be of particular application in the operation of various oil field equipment. Generally, one man is designated on a drilling rig as the driller to more or less superintend and direct the operation of the various machines used on a derrick iioor. Of course, in the drilling of wells, it is necessary to add additional lengths of pipe to the drill string as the drilling progresses. To this end a pipe rack is generally provided adjacent the drilling rig so that the pipe may be moved into position in the derrick as needed. To move this pipe into position, a cathead is provided which the driller operates around which is engaged one end of a cable or rope with the other end of such cable or rope attached to the pipe which is to be moved. The cathead is rotated by suitable power means such as compressed air or the like so that the engaged rope is reeled thereon to lift the pipe and move it in position. This operation is somewhat dangerous in that constant controls must be provided for the cathead in case someone should become entangled in the cable or rope engaged about the pipe. The instant invention is therefore provided so that the driller can control operation of the cathead while normal drilling operations proceed.

Another object of the invention is to provide a movable safety switch which is provided with rollers so that it moves out of engagement with the foot or hand of an operator whereupon the flow of power to the mechanism controlled by the operator is cut off.

Still another object of the invention is to provde a safety switch comprising a housing including side and bottom and top walls with the side and end walls forming a support to maintain the upper and lower plates or top and bottom walls in xed spaced relation, a plunger resiliently mounted in said housing and extending upwardly through the top plate, said plunger adapted to move up and down to regulate the flow or power through the safety switch to an operating mechanism.

Still a further object of the invention is to provide in a safety switch xed upper and lower plates retained in spaced relation by supports with the upper plate inclined rearwardly and toward the lower plate to form a foot rest, a spring supported plunger in said housing and extending upwardly through said top plate, a power conduit connected into said housing, said plunger movable to start and stop the flow of power through said conduit.

Yet a further object of the invention is to provide in a safety switch fixed upper and lower plates retained in spaced relation by supports with the upper plate inclined rearwardly and toward the lower plate to form a foot rest, a spring supported plunger in said housing and extending upwardly through said top plate, a power conduit connected into said housingy a contact aligned with said plunger and mounted in said housing, a circuit including electrical conduits extending into said housing and connected to said contact and plunger, said plunger normally retained in retracted position relative to said contact but movable to engage said contact to close the circuit between said plunger and contact and connecting electrical conduits.

Still a further object of the invention is to provide in a safety switch ilxed upper and lower plates retained in spaced relation by supports with the upper plate inclined rearwardly and toward the lower plate to form a foot rest, a spring supported plunger in said housing and extending upwardly through said top plate, a power conduit connected into said housing, a valve in said conduit, said plunger movable against said spring to open said valve and power conduit.

Other and l.further objects of the invention will become more readily apparent from a consideration of the following description and drawings wherein:

Fig. l is a perspective view illustrating the preerred embodiment of the invention;

Fig. 2 is a vertical side section showing the invention adapted for use with electrical conduits;

Fig. 3 is a vertical sectional View on the line 3-3 of Fig. 2;

Fig. 4 is a vertical side section illustrating the invention adapted for use as a nuid power conduit;

Fig. 5 is a top plan view modified form of the invention;

Fig. 6 is a side elevational View of the form of the invention shown in Fig. 5; and

Fig. 7 is an enlarged detail or" construction of the invention illustrated in Figs. 5 and 6.

In Fig. l the invention is shown as comprising the housing denoted generally by the numeral 2, such housing including end walls 3 and 4, side walls 5 and (i and top walls or plate 1 and bottom plate or wall 8.

The end walls 3 and 4 and side walls 5 and 6 form a support to maintain the upper plate 1 and lower plate 8 in fixed spaced relation.

As illustrated more clearly in each of Figs. 3 and 4, the top plate l is inclined from the front end It of the housing rearwardly and towards the lower plate to form a foot rest on top of the housing. A portion l2 of the end plate 4 extends upwardly above the plane of the foot rest to serve as a stop for the heel of the operator. Secured to and supporting the housing are the wheels l5. A support plate It is secured in the housing in any suitable position and as shown is secured to the upper plate Spring means Il are secured to such support by any suitable means such as screws IS extending through one end I9 of the spring while the other end 2|) of the spring means is engaged with the plunger 2| extending upwardly through the top plate of the housing. The spring means Il in cooperation with the support I6 resiliently mount the plunger in the housing for up and down movement therein through the opening 22 provided in the top plate A pad or cushion 23 may be secured to the upper end 24 of the plunger 2|. In the form of the invention illustrated in Fig. 2 a contact 23 is mounted on the bottom plate il of the housing 2 and is aligned with the plunger 2| A. power conduit 24 in the form of electric wires 25 and 26 extend into the housing to the post 28 which is provided with terminals 23, and 3|. The lead 2li is secured to the terminal 3| and then is secured to the contact 23 as illustrated at 32. The electrical lead 26 is connected to terminal 30 and extends through the conduit 34 where itis secured to the mechanism to be actuated when the safety switch is closed. Electrical lead 35 extends from the operating mechanism back to terminal 29 and is then connected as illustrated at 36 to the lower end 3T of plunger 2|. When the lower end 31 with the electric conducting material 38 is engaged with the electric conducting material 39 on contact 23, the circuit is closed between the input power conduit 24 and output power conduit 34. So long as the plunger and contact remain engaged, power will be supplied to the mechanism to which output power conduit 34 is connected and to which power is being supplied. The conducting material 38 is insulated from the end 3`| of plunger 2| and conducting material 39 is insulated with respect to contact 23 to prevent a short circuit between plunger 2| and contact 23 when they are engaged.

The wheels |5 may be mounted to roll on the track. 35 if desired, to prevent the safety switch from rolling helter-skelter when it is actuated.

While, it is believed that the operation of the invention is apparent by reason of the foregoing explanation, the following is given by Way of amplification and illustration.

To supply the power through the switch, the operators foot is placed upon the foot rest to depress the spring This moves plunger 2| downwardly into engagement with the contact 23 whereupon the circuit is closed and power is supplied to whatever mechanism is connected on the end of conduit 34. So long as the ma.- chine continues normal operation, it will be unnecessary for the operator to remove his foot from the foot rest and the strength of the springs i? is such that no great pressure need be exerted by the operators foot to overcome them and move the plunger 2| downwardly. Normally if a person receives an electric shock or if some part of his clothing or his hands become entangled in a machine which he is operating, there is a tendency to jump or move the legs. When this occurs, the springs I1 move the plunger 2l upwardly out of engagement with the contact 23 thereby opening the circuit 34. It is to be noted that the switch is therefore designed to take advantage of a natural impulse or movement on the part of the operator to move his legs upon the occurrence of some unnatural event. It is unnecessary for the operator to take any premeditated course of action to open the safety switch since it functions as a result of the removal of the pressure on the plunger 2| when the operator moves his leg. This action is further enhanced by the provision of the Wheels l5 which automatically move the device away from the operators foot upon the sudden impulse or move- .ment of the operators leg. Heretofore, safety devices have been. mounted in a stationary manner so that it was necessary for the operator to release the pressure on the switch so that it would be actuated. However, since the instant invention is mobile, any movement of the operator will tend to increase the possibility that the housing 2 will move thereby relieving pressure on the plunger 2| to actuate the switch.

The modification `of the invention illustrated in Fig. 4 is particularly adapted to be used in various mechanisms in the oil eld where a lluid pressure such as compressed air or the like is relied upon as the power source. In Fig. 4 the support I6 is provided with the springs Il secured thereto and engaging the plunger 2| as indicated at 2|. The plunger 2| extends upwardly through the housing as previously described and is terminated by the pad 23 adapted to receive the operators foot on the foot rest A valve body 40 is provided in the housing which has the downwardly facing seat 4| therein. Valve 42 is provided with the surface 43 arranged to engage on the seat 4| and has the upwardly extending stem 44 aligned with plunger 2|. The power conduit 24, in the case of pressure fluid may assume the form of a hose or pipe which is secured into the valve body 4U above the seat 4| as illustrated at 45. The power output conduit 34 will of course be of a similar form and is secured in the valve body below the Seat 4| as illustrated at 45. A spring 41 is provided in the valve body to engage valve 42 and normally retain such valve in closed position on the seat 4|. This prevents the flow of pressure fluid from the conduit 24 to conduit 34. The 0peration of the switch is similar to that previously described so that when the plunger 2| is moved downwardly it engages valve stem 44 and depresses spring 41. This permits free flow of pressure iluid from conduit 24 to conduit 34. If for any reason an emergency should arise, release of the plunger 2| would move valve 42 upwardly to stop the i'low between conduit 24 and 34 by engaging the seat 4|.

The additional safety feature of providing a mobile housing l. is also contemplated in the modication illustrated in Fig. 4. It is contemplated that the invention would be positive in its action since it can be kicked out of the operators way upon movement of the foot. This would insure that the flow of power would be stopped.

In the form of the invention illustrated in Figs. 5, 6 and 7, the trackway 35 is in the form of a slab 5|) which is longitudinally grooved as illustrated at 5|. The bottom 8 of the housing 2 is provided with depending knife contacts 53 aligned with grooves 5| in the track 35. The housing is positioned on the trackway 35 by pins or rollers 54 engaging in slot 55 in the edge 55 of trackway 35'. The bottom 51 of groove 5| is lined with a conducting material 58, extending from the point 59 adjacent end 50 of the trackway, while portion 59 of the groove is nonconducting. The conducting material 58 is suitably insulated from the bottom 51 of the groove and sides 59 to prevent short circuits.

In this form of the invention the electrical leads are connected into the conducting material 58 of trackway 35 as illustrated at 6| and 62. The knife contacts 53 are connected by wires 63 to the post 28, so that when knife contact 53 is in engagement with conducting material 58 in groove 5| with plunger 2| depressed, current will flow through the switch as previously explained herein, and so long as the knife contacts remain in the portion of the groove 5| where the conducting material is located, power will be transmitted. However, when the switch and knife contacts are moved to the portion 59 of grooves 5|, regardless of the position of plunger 2|, the switch will be opened and no power will be transmitted.

In this form of the invention, movement of the switch along trackway 35 past a predetermined point either stops or starts the iiow of power through the switch. The construction of knife or blade contacts 53 is such that any foreign substance is removed from the conducting material 58 which would tend to inhibit operation of the mechanism or which would inhibit move-= ment of the switch along the trackway.

Broadly the invention relates to a mobile safety switch construction.

What is claimed is:

A safety switch comprising a housing, said f' housing including side walls, end walls, bottom and top walls with each of said side and end walls connected to said bottom and top wall to retain said bottom and top wall in fixed spaced relation forming said housing, said top wall inclined rearwardly of said housing toward said bottom wall, a plunger extending upwardly through said top wall, a support secured in said housing for said plunger, leaf springs secured to said sup port and engaged with said plunger to resilient- 1y mount said plunger on said support, a contact aligned with said plunger and mounted in said housing, a circuit including electrical conduits extending into said housing and connected to said contact and plunger, said plunger normally retained in retracted position relative to said contact but movable to engage said contact to close the circuit between said plunger and contact and connected electrical conduits, wheels mounted on said bottom wall to support said housing, and a track on which said wheels roll, whereby the operator of said switch may roll the sitclzgh along the track as a reflex action due to s oc HARRY A. LOCEY.

Diehl Dec. 25, 1923 Mix June 13, 1950 Number 

